1. Field of the Invention
The present invention relates to a technique of positioning an optical fiber, and more particularly, to a technique of positioning an optical fiber in the axial direction.
2. Description of the Related Art
Patent document 1 (Japanese Patent Application Laid-Open No. H05-224045) discloses a method of contacting an end face of an optical fiber to an end face of an optical waveguide, as a method of positioning the optical fiber in the axial direction.
Further, patent document 2 (Japanese Patent Application Laid-Open No. H05-241047) and patent document 3 (Japanese Patent Application Laid-Open No. 2002-357737) each disclose a method of contacting a positioning wall or a positioning member to a part of an end face of an optical fiber, as a method of positioning the optical fiber in the axial direction. Patent document 4 (Japanese Patent Application Laid-Open No. 2005-164886) discloses a positioning method of contacting particularly a part of a diagonally polished end face of an optical fiber to the positioning wall of a fiber guide.
Patent document 5 (Japanese Patent Application Laid-Open No. 2003-43270) describes a method of forming an end of an optical fiber having a rod-like lens on the end face. Patent document 6 (Japanese Patent Application Laid-Open No. 2005-165016) describes a method of diagonally polishing an end face of an optical fiber having a lens.
In the method of patent document 1, the overall end face of an optical fiber is contacted to an end face of an optical waveguide to optically couple the optical fiber to the optical waveguide. Therefore, the method of patent document 1 cannot be applied to an optical module of spatial propagation type in which light emitted from an installed optical fiber propagates through the space.
In contrast to the method of patent document 1, in the methods of patent documents 2 and 3, a positioning wall and the like are contacted only to a part of an end face of an optical fiber and do not shade the light emitted from the optical fiber. Therefore, the methods of patent documents 2 and 3 are applicable to an optical module of spatial propagation type as well. However, the methods of patent documents 2 and 3 cannot be applied to an optical module including an optical fiber end having a diagonally polished end face which is frequently used to deal with reflected and returned light. For this reason, the applicant of the present application has proposed the method of patent document 4 beforehand in which positioning can be performed by contacting a part of a diagonally polished end face of a fiber to the positioning wall of a fiber guide.
In the method of patent document 4, however, the orientation of the axis of a spatial propagation of light which is incident on or emitted from an end face of an optical fiber is limited to ones parallel to the plane of a substrate having a fiber guide provided thereon. In other words, the method of patent document 4 cannot be applied to a module for achieving coupling of light to an optical element by making the light impinge upon or emit from it in an orientation not parallel to the plane but, for example, vertically upward or downward with respect to the plane of the substrate. In fact, an inclined contacting wall surface in accordance with that orientation is unable to be formed in substrate by means of ordinary etching techniques applicable for substrates.
In other words, first, the related art has no means for easily positioning an optical fiber end having a diagonal end face, in the axial direction at a given rotation angle while using the axis of the optical fiber as a rotation axis.
Further, in the methods of patent documents 2 to 4, it is necessary to contact a positioning wall and the like to at least a part of an end face of an optical fiber. Thus these methods cannot be applied to positioning in a process of connecting a rod-like lens to an end face of an optical fiber according to patent document 5 or positioning in a process of diagonally polishing an end face of an optical fiber end having a lens according to patent document 6. For this reason, in these processes, there is no other way but to visually recognize a fusion spliced interface of different kinds of optical waveguide members (an optical fiber and a rod-like optical waveguide which is a material of a rod-like lens) and determine a positioning reference for working these members. However, it is not always easy to visually recognize the fusion spliced interface of these members based on a small difference in index of refraction between these members.
In sum, secondly, the related art has no easily recognizable visual marker means, other than the fusion spliced interface, that serves as a positioning reference during the process of providing a rod-like lens to an end of an optical fiber or further polishing the end or it.
The present invention is designed in consideration of this point. An object of the present invention is to provide a technique capable of easily positioning an optical fiber in the axial direction without contacting a member to an end face of the optical fiber or visually recognizing a small difference in index of refraction between different kinds of optical waveguide members, while optionally adjusting the rotation angle of the optical fiber particularly even when the optical fiber has a diagonal end face.